1. Field of the Invention
The present invention relates to a lens apparatus for a surveillance camera, and more particularly, to a lens apparatus for a surveillance camera where a locking mechanism is provided in an operation ring which effects zooming or focusing.
2. Description of the Related Art
In lens apparatuses for surveillance cameras where zooming and focusing are manually performed, locking mechanisms are provided in zoom and focus operation rings such that set zoom and focus positions are not moved.
A conventional locking mechanism locks an operation ring by inserting a knob screwed on an outer peripheral part of the operation ring toward a lens barrel body and thereby pressing a distal end part of the knob against an outer peripheral surface of the lens barrel body (for example, Japanese Patent Application Laid-Open No. 2007-310228).
When the operation ring is locked by pressing the distal end part of the knob against the outer peripheral surface of the lens barrel body as described above, the lens barrel body is deformed, thereby affecting the optical performance.
Japanese Patent Application Laid-Open No. 2004-54186 discloses a method for locking an operation ring by attaching a stopper plate to a distal end of a knob screwed on an outer periphery of the operation ring, and pressing the stopper plate against an inner wall surface of a groove formed in a lens barrel body.
However, the method disclosed in Japanese Patent Application Laid-Open No. 2004-54186 has a disadvantage that it is complicated to assemble the apparatus since a shaft part is formed at a distal end of a threaded part formed on the knob and the stopper plate is rotatably supported on the shaft part.